Deletion of seven amino acid residues from the γ subunit of Escherichia coli H +-ATPase causes total loss of F1 assembly on membranes

Abstract

A mutant gene for the γ subunit of H +-translocating ATPase was cloned from Escherichia coli mutant NR70 isolated by B. P. Rosen [ J. Bacteriol. 116, 1124–1129 (1973)] . Determination of its nucleotide sequence revealed a deletion of 21 base pairs between nucleotide residues 64 and 84, resulting in a deletion of seven amino acid residues ( ▪) from the amino-terminal portion. This deletion resulted in the loss of a hydrophobic domain of the subunit estimated by an analysis of its hydropathic character. Since F 1 subunits are reported not to be assembled on the normal F 0 portion of NR70, it is concluded that the hydrophobic domain deleted in the mutant subunit is important for assembly of the F 1 portion. Introduction of a plasmid pNR70 carrying the mutant allele of NR70 into a wild-type strain gave no recombinants resistant to neomycin. This result suggested that the neomycin-resistant phenotype is not directly related to the defect in the γ subunit of NR70.